This invention relates generally to navigation guidance and, in particular to a method of navigation guidance for a remote communications node.
A distributed navigation system generally has a navigation server component where navigation data is stored and a client component for route guidance. The client component can be an in-vehicle device or some other portable wireless device with a method of determining position.
Prior art methods of providing navigation guidance for client components have numerous deficiencies. For example, existing navigation systems that download route data only download a single route from an origin point to a destination point. When the client component is moving, the client""s position changes between the time the route is requested and the time the route data arrives at the client. The client component may move a large distance during route download, and may in fact pass the first maneuver point on the route. If this happens, the entire route becomes useless and the client component must request a new route.
Another problem with this method occurs where there are numerous routes available from the starting location of the client component. Existing guidance systems will only provide one route from the starting location, which may not even be available or accessible to the user of the client component. This can occur in vehicle applications where the vehicle is in a parking lot and the beginning of the route downloaded starts on a street that is not accessible from the parking lot, or a median prevents the vehicle from turning on a street in the direction given by the route. The route then becomes useless and the client component must request a new route once underway on the roadway network, where the timing of route download outlined above can occur further compounding the problem.
Accordingly, there is a significant need for methods of navigation guidance that overcome the deficiencies of the prior art outlined above.